1. Field of the Invention
The present invention relates generally to the design and use of medical devices. More particularly, the present invention relates to a guide catheter which is useful for implanting cardiac pacemaker and defibrillation leads in the heart and coronary sinus.
Implantable cardiac pacemakers are widely used to treat a variety of cardiac conditions, particularly arrhythmias including both bradycardias and tachycardias. The use of pacemakers for defibrillation and other electrical therapies is also under development.
Implantable cardiac pacemakers require placement of electrical lead wires within the heart or coronary sinus, where the electrical leads may be connected to a remotely implanted pacemaking unit. Placement of the electrical lead wires can be accomplished either by open surgical techniques or by transvenous techniques. Of particular interest to the present invention, transvenous lead placement is accomplished by establishing percutaneous access to the venous system, typically via the subclavian vein, and passing the electrical lead to the desired target location within the heart, typically the right ventricular apex. The lead will include a self-anchoring mechanism at its distal end, typically a helix, screw, or tines, and the end of the lead wire can be engaged against and anchored in the endocardium.
Transvenous placement of the electrical leads for an implantable pacemaker can be problematic. At present, the leads are usually positioned using an internal stiffening stylet which is used to guide the distal end of the lead under fluoroscopic imaging. Since the leads lack column strength and there is substantial blood flow through the heart chambers, manipulating a lead is difficult and positioning of the lead is not always accurate. Thus, the physician must often disengage the lead anchor and reposition the lead one or more times before satisfactory placement is completed. It will be appreciated that such repositioning of the electrical lead can cause unnecessary trauma to the patient, with risk of causing arrhythmias and ventricular perforation.
The problem of positioning electrical leads for implantable cardiac pacemakers is partially addressed by electrical leads which have retractable lead anchors. See, for example, U.S. Pat. Nos. 5,129,404 and 4,924,881. Each of these patents discloses an electrical lead having a helical anchor which can be retracted within a body of the lead during introduction and initial placement of the lead within the heart. Alternatively, leads having a distal anchor protected by a soluble cover are available from Intermedics, Inc. Angleton, Tex. Such designs, however, can still be traumatic to the patient. The distal ends of the leads are blunt and can cause trauma when engaged against the endocardium. Moreover, the designs apparently do not allow for precise positioning since the patents contemplate that the anchor may be withdrawn back into the lead body one or more times for repositioning of the lead.
For these reasons, it would be desirable to provide improved methods and devices for implanting cardiac pacemaker lead wires within the heart. In particular, it would be desirable if such improved apparatus and methods addressed at least some of the deficiencies described above. More particularly, it would be desirable to provide apparatus and methods for accurately positioning electrical lead wires within the heart prior to implantation within the endocardium to reduce or eliminate the need for repositioning of the lead after implantation. It would be further desirable if the apparatus and methods were useful with conventional electrical leads so that the actual design of the pacemaker system need not be changed in any way.
2. Description of the Background Art
U.S. Pat. No. 4,166,469, describes an axially splittable introducer sheath which is used for introducing a pacemaker lead into the subclavian vein. The lead is pushed from the sheath to the heart. U.S. Pat. Nos. 5,129,404 and 4,924,881, described pacemaker lead wires having retractable helical anchors. U.S. Pat. No. 5,174,303, describes a pacemaker lead wire having a replaceable stylet with a distal sensor element. U.S. Pat. No. 5,228,455 describes a tool for implanting lead wires for pacemakers. Other cardiac electrodes and lead wires are described in U.S. Pat. Nos. 5,282,845; 5,228,455; 5,170,803; 5,170,802; 5,029,585; 4,991,578; and 4,553,554. Peel-away sheaths having a breakaway hemostasis value are manufactured by Pressure Products, Inc., Rancho Palos Verdes, Calif. and sold under the tradename SafeSheath.TM..